Carburetor choke system



March 29, 1966 w. o. MANNING, JR 3,243,163

CARBURETOR CHOKE SYSTEM I Original Filed Oct. 1, 1962 uw. Q. mi b. Q

INVENTOR M//L 4M 0. M/V/V//l/G, e/.

20 ab 4'0 s'o ab United States Patent O 3,243,168 CARBURETOR CHOKE SYSTEM William 0. Manning, Jr., Livonia, Mich., assigner to Holley Carburetor Company, Warren, Mich., a corporation of Michigan p Continuation of application Ser. No. 227,466, Oct. 1, 1962. This application May 17, 1965, Ser. No. 461,585 3 Claims. (Cl. 261-46) This is a continuation of U.S. application Serial No. 227,465 entitled Carburetor Choke System and filed on October 1, 1962, in the name of William O. Manning, Jr., now abandoned.

This invention relates generally to internal combustion engine carburetors, and more specifically to the choke mechanism therefor. I

The purpose of a carburetor choke plate is to cut olf air flow and thereby increase the richness of the mixture during cranking when the engine is cold and during subsequent cold engine operation. While any particular choke construction may be adaptable for a number of engines, certain specific engines may require a leaner cranking mixture than other engines which use the same carburetor. For this reason, it has been the practice to trim off or drill holes through the vchoke plate so as to supply more air to the engine during cranking than if the holes were not provided.

One serious objection to the above mentioned modification of the choke plate is that it in effect reduces the choke plate area, and this effect is retained, although to an ever decreasing degree, until the choke plate is substantially wide open. the leaner cranking mixture that is provided by drilling holes in or trimming the choke plate, they also require a somewhat richer mixture than would be provided with a trimmed or perforated choke plate after the engine has started and the choke plate is partially open.

It Lhas been found that this intermediate condition can be provided by forming an opening not in the choke plate itself, but in the wall of the air intake passage in which the choke valve is pivoted, the opening being on the engine side of the closed choke plate so that the choke plate traverses the opening as it moves from the closed to the open position. In other words, additional air to lean out the cranking mixture is supplied through the proposed opening when the choke is closed, and this supply of additional air is progressively reduced in amount as the edge of the choke plate traverses the opening until the effect of the opening is eventually eliminated when the choke reaches some predetermined position, such as half open. With the proposed construction, the area of the choke plate is not reduced, yet the same initial leaning effect is obtained.

Accordingly, a primary object of this invention is to provide a means in lieu of the usual trimmed or perforated choke plate to insure proper starting and to additionally provide a correct fuel-air mixture at low engine temperatures.

Other more specific objects and advantages of the invention will become apparent when reference is made to the following description and accompanying drawings, wherein:

FIGURE 1 is a fragmentary elevational View in partial cross section illustrating a carburetor embodying the invention;

FIGURES 2 and 3 are graphs comparing the performance -of prior art carburetors with that of a carburetor embodying the invention;

FIGURE 4 is a fragmentary cross-sectional view taken on the plane of line 4-4 of FIGURE l and illustrating two modifications of the invention;

Referring to the drawings in greater detail, FIGURE While certain engines may require 3,243,168 Patented Mar. 29, 1966 l illustrates a carburetor body 10 mounted on an engine intake manifold 12 and having an induction passage 14 including a choke plate 16, a main fuel nozzle 18, a venturi 20, and a throttle plate 22 therein. FIGURE 1 further illustrates the usual fuel reservoir 24 as an integral part of the carburetor body 10, as well as a mounting flange 26 for the usual air cleaner (not shown).

A single choke mixture opening 28 is formed through the Wall of the carburetor body 10 above-the mounting flange 26 for the air cleaner, and slightly below the lower edge of the choke plate 16 while it is in a fully closed position. The opening 28 may be of a calibrated size in order to obtain a desired fuel-air mixture, in conjunction with the movement of the edge of the choke plate 16 past the opening 28.

As seen in FIGURE 1, the opening movement of the choke plate 16 will vary to effective size of the opening 28 until such time as the choke plate 16 edge has passed to a point below the opening 28. Thus, it can be readily seen that an amount of air sufficient for proper starting, While the choke plate 16 is initially closed, is provided by the full opening. Then, as the choke plate 16 begins to move, the effective size of the opening 28 changes as described above, and a progressively diminishing amount of air is permitted to enter through the opening 28 into the induction passage 14 for mixing with the fuel being supplied by the usual fuel supply systems. Once the edge of the choke plate 16 completely passes the opening 28, no additional influence from the opening 28 will be felt in the induction passage 14.

The practical advantage of the invention can be readily determined by referring to FIGURES 2 and 3. As seen in FIGURE 2, the cranking mixture supplied in a particular carburetor-engine combination where a choke plate containing no perforated holes or reduction in area is used may have a fuel-air ratio when the choke is closed on the order of .87, as indicated by the dash line. However, during the cranking operation for some engines, it may be desirable to have a much leaner mixture, say on the order of .5 fuel-air ratio. It can be seen from FIGURE 2 that, in actual tests, a choke plate having perforated holes incorporated therethrough produced a satisfactory .53 ratio, as indicated by the dot-dash line. Likewise, tests with the same carburetor having the variable choke mixture opening 28 incorporated therein, in lieu of the holes in the choke plate itself, produced a satisfactory .46 fuel-air ratio, as indicated by the solid line. The opening 28, of course, may be calibrated to produce the exact fuel-air ratio desired. If a single opening 28 producing the desired cranking mixture were found to produce an undesired slight leaning effect during part throttle operation a horizontal slot A or a series of horizontally ailgned smaller holes B having the same total area could be substituted for the single larger drilled opening 28, as shown by FIGURE 4.

In FIGURE 3, the effect of the above mentioned prior art structures during part throttle operation is compared with the effect resulting from a carburetor utilizing the invention. The dash line curve is indicative of the part throttle result which may be desired in a particular carburetor-engine combination, and which would be obtained from a standard carburetor having a choke plate which does not have trimmed edges or holes formed therein and which does not include an opening 28. It can be seen from the dot-dash curve of the figure that the perforated choke plate, which was shown above to have produced a desirable cranking mixture, produces much too lean a fuel-air mixture during the early part throttle positions, as compared to the optimum dash line curve. Referring now to the solid line curve, which is representative of the result obtained when the invention is used, it can be seen that the result during all phases of part throttle flow compares very closely with the optimum flow dash line curve.

It should be readily apparent that a novel and simple means has been provided for supplying a correct amount of air during both the cranking and part throttle starting low engine temperature operations, hence eliminating the disadvantage resulting from having holes drilled through the choke plate itself, as has been the heretofore conventional practice in order to satisfy particular engine requirements.

It is apparent that other modifications of the invention may be made without exceeding the scope of the appended claims.

What I claim as my invention is:

1. An internal combustion engine carburetor, comprising an induction passage having a venturi, a pivotable throttle valve |positioned posterior to said venturi for controlling the ow of combustible mixture to said engine, a main fuel nozzle positioned near said venturi, a pivotable choke valve in said induction passage anterior to said venturi for controlling the flow of air to said carburetor, and a separate constantly open air passage communicating with said induction passage and controlled by the operation of said choke valve for supplying a predetermined quantity of air to said carburetor during cranking of said engine, said air passage being positioned closely adjacent the downstream side of said choke valve when said choke valve is fully closed so as to be on the engine vacuum side yof said choke valve when said choke valve is fully closed during cranking and on the atmospheric side of said choke valve when said choke valve is partially opened upon engine starting, `said air passage thus being rendered inoperative to supply air by opening movement of said choke valve to a partially opened position, the effect of said air passage being to lean out the closed choke cranking mixture supplied to said engine.

2. In an internal combustion engine carburetor adap-ted to be fitted with an air cleaner, an induction passage having a choke plate, a main fuel nozzle, a venturi and a throttle plate therein, and a constantly open choke mixture hole formed through a wall of said carburetor located within the aircleaner and positioned closely adjacent the downstream side of said choke plate when fully closed for supplying a variable colume of clean air to said induction passage during low temperature closed-choke cranking, the edge of said choke plate being movable past said hole as said choke plate partially opens.

3. An internal combustion engine carburetor, comprising an induction passage having a pivotable choke plate offset to open in response to air flow to the engine, a venturi and a throttle plate,.an aircleaner flange extending from the outer surface of said body on the downstream `side of said choke plate, a constantly open opening through the wall of said induction passage between said choke plate when closed and said aircleaner ange so that -only clean air can enter said opening, said opening being positioned closely adjacent the downstream side of said choke pla-te when said choke plate is fully closed, the relationship between said choke plate and said opening bein:y such that a plane extending through said opening perpendicular to the axis of said induction passage is intersected by said choke plate when said choke plate first opens on starting of the engine.

References Cited by the Examiner UNITED STATES PATENTS 1,767,664 6/1930 Geiger 261-46 X 1,968,553 7/1934 Heitger 26l39 2,025,867 l2/1935 Hopes 261-64 X 2,408,349 9/1946 Stanton 261-39 X 2,998,231 8/1961 Marsee et al. 261--39 X HARRY B. THORNTON, Primary Examiner.

T. R. MILES, Assistant Examiner. 

1. AN INTERNAL COMBUSTION ENGINE CARBURETOR, COMPRISING AN INDUCTION PASSAGE HAVING A VENTURI, A PIVOTABLE THROTTLE VALVE POSITIONED POSTERIOR TO SAID VENTURI FOR CONTROLLING THE FLOW OF COMBUSTIBLE MIXTURE TO SAID ENGINE, A MAIN FUEL NOZZLE POSITIONED NEAR SAID VENTURI, A PIVOTABLE CHOKE VALVE IN SAID INDUCTION PASSAGE ANTERIOR TO SAID VENTURI FOR CONTROLLING THE FLOW OF AIR TO SAID CARBURETOR, AND A SEPARATE CONSTANTLY OPEN AIR PASSAGE COMMUNICATING WITH SAID INDUCTION PASSAGE AND CONTROLLED BY THE OPERATION OF SAID CHOKE VALVE FOR SUPPLYING A PREDETERMINED QUANTITY OF AIR TO SAID CARBURETOR DURING CRANKING OF SAID ENGINE, SAID AIR PASSAGE BEING POSITIONED CLOSELY ADJACENT THE DOWNSTREAM SIDE OF SAID CHOKE VALVE WHEN SAID CHOKE VALVE IS FULLY CLOSED SO AS TO BE ON THE ENGINE VACUUM SIDE OF SAID CHOKE VALVE WHEN SAID CHOKE VALVE IS FULLY CLOSED DURING CRANKING AND ON THE ATMOSPHERIC SIDE OF SAID CHOKE VALVE WHEN SAID CHOKE VALVE IS PARTIALLY OPENED UPON ENGINE STARTING, SAID AIR PASSAGE THUS BEING RENDERED INOPERATIVE TO SUPPLY AIR BY OPENING MOVEMENT OF SAID CHOKE VALVE TO A PARTIALLY OPENED POSITION, THE EFFECT OF SAID AIR PASSAGE BEING TO LEAN OUT THE CLOSED CHOKE CRANKING MIXTURE SUPPLIED TO SAID ENGINE. 